A Hybrid Touch Interface for Prêt à Voter Chris Culnane, University of Surrey Trustworthy Voting Systems Project Overview • Brief Introduction to Prêt à Voter • Motivation • Hybrid Touch Concept • Implementation Prototypes • Future Work Voting in Prêt à Voter • Fill in ballot form • Detach and destroy Left Hand Side • Submit Right Hand Side to the system (scan) • Receive signed receipt from Web Bulletin Board (WBB) • Right Hand Side is published on WBB Properties • Privacy – The Right Hand Side does not reveal how you voted – No machine learns how you voted • End-to-end verifiability – Voters can check the inclusion of their vote – 3rd parties can check each operation • Strong integrity guarantees • Accessibility? Accessibility of Voting in the UK • Limited – Tactile Voting Device (2001) • Polls Apart Campaign – Reports after each election – Works with Electoral Commission Motivation • Accessibility is a requirement of any new voting scheme in the UK • Round table discussion with Polls Apart 2010 • Polls Apart Report 2010 recommendation: – “Ensure disabled people can vote independently and in secret by diversifying voting methods...” Motivation • We often have to make a pragmatic choice about accessibility and privacy – If we want the system to help the voter cast their vote, it generally has to learn how they vote • Can we develop a front-end, for Prêt à Voter, which does not compromise on privacy? Previous Ideas • Previously suggestions have been to line up a left hand side paper ballot with a touch screen – Not really usable, let alone accessible Hybrid Touch Concept • Maintains the concept of two halves of a ballot paper • Left hand side is paper based • Right hand side is digital – rendered on a touch screen or Surface Computer • How it works: – Detect location and orientation of left hand side – Render right hand side in appropriate location – User interacts by touching virtual right hand side What are the advantages? • Machine does not learn how voter has voted • Additional accessibility equipment can be added to assist in the vote casting (Large buttons, sip and puff, voice control, etc.) • Automatic validation of correct entry • No scanners – No need to interpret human handwriting/OCR • The process of voting is entirely completed within the booth Implementation - Microsoft Surface • Natural User Interface • Interacting with everyday objects • Microsoft Surface consists of: – direct interaction – multi-touch contact (50 touches) – a multi-user experience – object recognition via Identity Tags How Does Microsoft Surface Work? http://www.popularmechanics.com/technology/industry/4217348.html?page=2 Example Microsoft Surface – Ballot Paper • Easy to construct • Standard Prêt à Voter ballot paper – Additional Identity Tag on underside – Contains same information as Right Hand Side barcode – Identity Tag used for orientation and location Front Back Microsoft Surface Implementation - Microsoft Surface • Expensive – approximately £10,000 • Large and immobile – Practical issues of locating them – No easy way to adjust height 3M Multi-Touch - Projected Capacitance • 3M Multi-Touch can handle 20 touches (M2256PW) • Similar technology as on modern mobile phones • Two layers of perpendicular wires • A charge is applied creating capacitance at the intersections • Bringing a finger or conductive stylus within the electrostatic field causes a change in the capacitance • This change is used to identify the location of the touch Projected Capacitance Technology • How we could use it: – Use conductive ink/foil marks on the underside to simulate touches – Define a template of simultaneous touches that indicate a ballot (currently a rectangle of a specific size) – Use these touches to determine location and orientation Projected Capacitance 3M Multi-touch screen – Foil backed card – Conductive foam pads (6mm) – Able to locate and orientate a left hand side – Display virtual right hand side Screen Projected Capacitance Ballot Projected Capacitance Projected Capacitance • Cheaper and more flexible • Currently still need to scan a barcode to acquire serial number – Looking into using multiple conductive pads in a sparse matrix on the underside to provide that information • Ballot paper is more difficult to construct Microsoft Surface – Version 2 • Samsung SUR40 with Microsoft PixelSense • Only 103mm thick – Can be mounted on an arm for adjustment Summary • Developed an interface that provides some accessibility without compromising privacy • Proof of concept – Microsoft Surface – Multi-touch screen Future Work • Further work needed to polish user interface • Reduce size of conductive pads • User Trials QUESTIONS?.